Environmental, health & safety concerns. The plasma in medium-pressure mercury lamps generates considerable heat, and the bulbs are vulnerable to breakage that can expose the environment to toxic materials. Disposal of mercury-based lamps is a significant and growing problem. Mercury lamps emit short wavelength UV, which can cause skin and eye damage if not operated properly. They also generate toxic ozone that must be exhausted.

Cause process variability. Use of lamps can cause heat damage to parts, while degradation of light over life and bulb-to-bulb variability can produce inconsistent process results.